A concentration photovoltaic module (CPV) essentially comprises a photovoltaic cell (for example, multi-junction) and a concentrator designed to concentrate solar radiation toward the cell.
In the case of a multi junction cell, the different junctions are arranged in series, each of the junctions being adapted to a specific spectral band of the solar spectrum.
Multi junction cells, which are a smaller size than conventional solar cells made of silicon, have the advantage of offering better efficiency, but to function, need a higher light intensity.
In a CPV module, the cells are associated with a concentrator, for example, a Fresnel lens, which concentrates solar radiation toward the cell.
Also, photovoltaic modules are designed to be mounted on a sun-follower system (also called “tracker”) so as to optimally orient the module as a function of the trajectory of the sun so that the concentrators focus the rays of the sun onto the cells.
During manufacture of such photovoltaic modules, it is usual to verify the operation and performance of each module, with a view to detecting any failure of any one of the junctions, defects in quality or positioning of concentrators, or any other anomaly of the module before it is shipped.
The modules are frequently combined by being mounted totally or partially in series. In this case, performance of the overall system will be limited by the weakest element. It can, therefore, prove useful to select the modules before they are combined so that they are homogeneous in response. In this respect, it is important to be able to measure the performance of this module.
For this purpose, it is known to simulate the lighting of the sun by means of a lighting device generally called “flasher,” which generates a light beam having irradiance, spectral power distribution and angular divergence close to those of the sun. These characteristics are to conform over the entire surface of the module to be tested.
CPV modules currently commercially available have relatively small dimensions (of the order of 0.5 to 1.5 m2). There are lighting devices that simulate solar lighting on a module of this type.
The Soitec company has marketed large-size solar modules, having a surface of several m2, comprising several CPV modules connected by a single chassis.
So, for example, a module of 8 m2 can be formed by two rows of six sub-modules, which can optionally be connected in series.
There is, therefore, the problem of being able to test a large-size module. In fact, since the sub-modules are connected totally or partially in series and their mechanical integrity is assured by a single chassis, they cannot be tested independently.
On the other hand, it is important to ensure the operation of the assembly before it is installed.
It is, therefore, necessary to be able to verify the performance of the complete module by simulating lighting that is closest to solar radiation.
In this respect, the constraints the lighting device must respect are the following:                irradiance comparable to that produced by the sun at ground level, that is, of the order of 1 kW/m2,        reproduction of the complete solar spectrum, from ultraviolet to infrared, by respecting spectral densities,        angular divergence close to that of solar light, that is, 0.5° (±0.25°), and        considerable spatial uniformity of the irradiance (the aim being inhomogeneity of irradiance less than or equal to 5%).        
Known lighting devices do not respond to these demands for a large-size module.
In fact, these devices offer either a more reduced field or characteristics (especially angular divergence) too far removed from those of the sun.
Such characteristics on extended fields of the order of a square meter to a few square meters with a single light source are possible to reproduce only over very short periods with flash lamps.
In fact, the power necessary to produce irradiance of the order of 1 kW/m2 on a surface of the order of the m2 would be too great to be continued (power consumption would then be very high with consequent heating of the system).
Flash lamps are generally used in this type of lighting device as they reach sufficient intensity to test the photovoltaic modules.
Another constraint to be considered in designing the lighting device is the compactness of the test installation.
So, it is not feasible to place a light source far from the module to obtain low angular divergence because, given the surface of the module, this would imply a distance of several tens of meters not compatible with an industrial installation.
It might be feasible to use several known devices that would illuminate each part of the module.
However, the problem of synchronization of light sources comprising flash lamps producing different beams arises.
In fact, light sources produce light pulses and the measurement of performance of the module is recorded during these pulses.
So that measurement can be carried out, pulses, therefore, have to be produced at the same instant for all of the light sources, that is, the sources are synchronized in a range of the order of a few hundreds of μs.
Flash lamps of light sources are supplied by condenser batteries.
There is, therefore, a delay between triggering of the source and emission of the pulse, which is greater than the preferred range of synchronization.
This delay is variable from one source to the other.
It can be due to the impedance of the electric triggering circuit, or to delays due to the differences of clocks of triggering cards.